A series of private WhatsApp messages between Brittany Higgins and David Sharaz allegedly showing the pair colluding over a defamatory tweet could lead Liberal Senator Linda Reynolds to expand her legal case against her former staffer.

The former defence minister, who plans to retire from politics at the next election, is suing Ms Higgins over social media posts she says have damaged her reputation.

During a hearing for the high-profile case in the WA Supreme Court on Friday, Reynolds’ legal team said Higgins and Sharaz debated who should publish her fiance’s now-deleted tweet based on the number of social media followers each had.

“There was a discussion – whose Twitter account was the better one to post on,” Senator Reynolds’ lawyer, Martin Bennett, told reporters outside court.

“That indicates that they weren’t acting independently of each other and we say to the court, that’s the argument that we want to advance.”

Bennett said Reynolds would ask the court’s permission to amend her claim against Higgins to include the tweet from January 2023 on the basis that she was also a publisher.

Reynolds’ legal team also raised concerns about the “significant shift” in Ms Higgins’ defence, which has been amended.

Bennett said there were paragraphs about “justification of contextual truth” that he could not understand.

“For example … it said that Senator Reynolds asking (her then chief of staff Fiona Brown) to lodge a complaint with the police was a mishandling of the rape allegation,” he said.

Bennett said he would consider applying to the court to strike out the paragraphs.

The court also heard Sharaz had consented to judgment after tweeting in April that he would no longer fight Reynolds’ allegation that he had also defamed her in a series of social media posts.

The order required Sharaz to delete three tweets, a Facebook post and an Instagram story from 2022 and 2023, which his lawyers said had been done.

The damages Sharaz will have to pay following his admission will be decided after Higgins’ defamation trial later in the year.

-AAP